A technology used in an object recognition apparatus is known, in which a first image plane and a second image plane of different points of view are created by two cameras arranged parallel to one another on the left and right with a predetermined space in between; the amount of displacement between corresponding parts of the object image in the respective image planes is calculated; and the perpendicular length from the object to a straight line that connects the left and right cameras is found based on the amount of displacement using the principle of triangulation (for example, refer to Patent Document 1). With this object recognition technology, it is necessary to arrange the left and right cameras in an accurate position so as to obtain a stereo image; deviation in the position of the left and right cameras leads to error in the calculation of position coordinates. When such an object recognition apparatus is mounted on an automobile or the like, the degree of freedom with which the cameras can be positioned is not high, and therefore it is necessary for the accuracy of the camera mounting to meet stringent conditions.
A technology is known in which a first image plane and a second image plane of different points of view are created from images captured by a single camera before and after movement; the amount of displacement between corresponding parts of the object image in the first image plane and the second image plane, conversion processing compensating for the camera movement having been performed on the second image plane, is calculated; and the perpendicular length from the object to a straight line that connects the left and right cameras is found based on the amount of displacement using the principle of triangulation (for example, see Patent Document 2). With this object recognition technology, image planes from before and after movement of a single camera are used, and thus accuracy in mounting the camera is not particularly demanded. However, in order to find the position coordinates of the object, the position coordinates of the object are calculated based on the amount of displacement between corresponding parts of the object image in the first image plane and the second image plane, and the object is reconstructed; therefore, there is a problem in that the structure of the curved surface portions of the object cannot be reconstructed. Note that this problem also arises in the technology disclosed in Patent Document 1.
A method is known, in the technological field called “computer vision”, in which, when finding the fundamental matrix (also called “F-matrix”) as a conversion matrix of points corresponding between two images obtained from different points of view, 8 pairs of corresponding points are first taken at random from N pairs of corresponding points, and using the F-matrix found using the 8 pairs of corresponding points, an epipolar line for points in the second image plane that correspond to the points in the first image plane is calculated. Next, a series of processes, in which a distance d between the corresponding points in the second image plane and the epipolar line is found, and the discrete value of pairs of corresponding points in which the distance d is not greater than a certain threshold value is found, is repeated for a set number of times while taking the 8 pairs of corresponding points at random, so that the final F-matrix is an F-matrix in which the discrete values are maximum (for example, refer to Non-Patent Document 1). With this method, not less than 8 pairs of corresponding points are necessary in order to find the F-matrix, and thus a problem arises, particularly when applying this method to an object recognition apparatus for a moving object such as an automobile, in that stable detection and tracking is difficult.
Patent Document 1: JP H5-114099A (paragraphs 0016-0020; FIGS. 3, 4, 5)
Patent Document 2: JP 2001-187553A (paragraphs 0042-0066; FIGS. 4 and 8)
Non-Patent Document 1: Torr, Philip: Motion Segmentation and Outlier Detection. University of Oxford: 1995, pp. 58-60.